BirdAnalyst
Species · BCR 4 · BBS 2025 Release · 1966–2024

Black-billed Magpie In BCR 4

All regionsBCR 4Generalists

Black-billed Magpie in BCR 4 has surged: up 98% on the route-weighted index since 1978.

+98%Since 1978TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
35Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
45YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Black-billed Magpie has surged in BCR 4: up 98% on the route-weighted index since 1978.

Black-billed Magpie In BCR 4 Population Forecast

If the recent trend holds, Black-billed Magpie in BCR 4 is projected to rise about 19% by 2029 — from 1.1 in 2024 to a central estimate of 1.4 (95% range 0.41–2.3). A 5-year backtest shows a typical error of ±12.4%, with 100% of held-out values landing inside the 95% band.

+19%Change by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
1.4Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.41–2.395% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±12.4%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Black-billed Magpie in BCR 4 is projected to rise about 19% by 2029 — from 1.1 in 2024 to a central estimate of 1.4 (95% range 0.41–2.3). A 5-year backtest shows a typical error of ±12.4%, with 100% of held-out values landing inside the 95% band.19762029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20251.30.402.3
20261.40.402.3
20271.40.402.3
20281.40.412.3
20291.40.412.3

Routes In BCR 4

Routes recording Black-billed Magpie in BCR 4.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
CohoeALASKA142023
KachemakALASKA142024
Anchor RiverALASKA132024
HomerALASKA91982
SavageALASKA72024
KalifonskyALASKA62023
ToklatALASKA52021
SourdoughALASKA52022
SlanaALASKA32024
Goose BayALASKA31982
Hatcher PassALASKA32024
CottonwoodALASKA31990
Mccarthy Rd2ALASKA31999
MaclarenALASKA21986
WasillaALASKA21983
Seven LakesALASKA22023
Ft. RichrdsnALASKA22017
Birch LakeALASKA12019
ChistochinaALASKA12022
MonahanALASKA12019
CantwellALASKA12015
Skilak LakeALASKA11985
WillowALASKA12024
Kenny LakeALASKA12019
Swan Lake RdALASKA12022

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.